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Silicon steel laminations are introduced as the back-plate to an electromagnetic acoustic transducer (EMAT) to increase the efficiency of the EMAT by increasing the magnitude of the EMAT coil's dynamic magnetic field and the eddy current in the sample surface. A two-dimensional, non-linear finite element model is developed to quantify the effectiveness of the back-plate’s different maximum permeability and saturation flux density, on increasing the eddy current density and the dynamic magnetic flux density in the specimen. A three-dimensional FE model is also developed, and confirms the expected result that the laminated structure of silicon steel (SiFe) markedly reduces the eddy current induced in the back-plate, when compared to a continuous slab of the steel. Experimental results show that silicon steel lamination can increase the efficiency of the EMAT in the cases both with and without a biasing magnetic field. [ABSTRACT FROM AUTHOR]

Abstract: This paper proposes an acoustic multi-touch tactile sensing method. The proposed method is based on an amplitude disturbed ultrasonic wave diffraction pattern. An A 0 Lamb wave transmitted in a thin finite copper plate is processed to provide tactile information, for one or two fingers. A touch event is localized by identifying the diffraction signals among a database of diffracted Lamb wave references. Statistic models are used to improve the localization reliability. An artificial silicone finger is used in the calibration procedure. This touch interface is evaluated as a 2-touch interface. [ABSTRACT FROM AUTHOR]

• TDTE high precision imaging of blind hole is realized. • Super resolution imaging of multiple blind holes is realized. • The imaging accuracy is better than the traditional ultrasonic Lamb wave imaging method. • It promotes the TDTE lamb imaging to industrial application. [Display omitted] Lamb waves are characterized by frequency dispersion and mode conversion. The imaging results obtained with traditional ultrasonic array imaging methods suffer from artifacts, reducing the imaging accuracy. In addition, traditional methods are subjected to the Rayleigh criterion and cannot image multiple defects with spacing smaller than the resolution threshold of ultrasound array imaging. In this paper, an ultrasonic Lamb wave inverse scattering topological imaging method based on time-domain topological energy (TDTE) was proposed. In this method, the topological progressive process of the inverse scattering topological imaging method was transformed into solving the direct and the adjoint sound fields. Then, by inverting the time of the adjoint sound field, the direct and the adjoint sound field can focus adaptively at the defect, which overcomes the influence of Lamb wave mode conversion and dispersion on the imaging results, and improves the imaging accuracy and resolution. Finally, the direct and the adjoint sound field are fused, and the TDTE value was taken as the pixel value of imaging. Accordingly, the limitation of the Rayleigh criterion was broken; the resolution of imaging was improved; the multi asymmetric defect imaging with the interval was realized less than the resolution threshold of the ultrasonic array imaging. The experimental results show that the TDTE method for multiple asymmetric defects can achieve super-resolution than the total focus method (TFM) and time-reversal (TR) method and can accurately distinguish the asymmetric defects when the defect spacing is smaller than the resolution threshold of the ultrasonic array imaging. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the design and modelling of ultrasonic tomography for two-component high-acoustic impedance mixture such as liquid/gas and oil/gas flow which commonly found in chemical columns and industrial pipelines. The information obtained through this research has proven to be useful for further development of ultrasonic tomography. This includes acquiring and processing ultrasonic signals from the transducers to obtain the information of the spatial distributions of liquid and gas in an experimental column. Analysis on the transducers’ signals has been carried out to distinguish between the observation time and the Lamb waves. The information obtained from the observation time is useful for further development of the image reconstruction. [Copyright &y& Elsevier]

• Utilized a Galfenol Rod Ultrasonic Transducer (GRUT) excite low-frequency ultrasonic guided waves in plate inspection. • Finite element simulation of GRUT to generate guided waves. • Detection methodology of "A0 for defect determination, S0 mode for location". • Introduce short-time Fourier transform (STFT) is to judge the converted mode of guided waves. Lower frequency ultrasonic guided wave (20 kHz–200 kHz) has obvious advantages in large area plate monitoring. It enables longer propagation distances because of low attenuation and simple modes. The present study utilized a Galfenol Rod Ultrasonic Transducer (GRUT) excite low-frequency ultrasonic guided waves in plate inspection. It was verified by finite element simulation and experiment that GRUT can excite S 0 mode Lamb wave, A 0 mode Lamb wave and SH 0 wave. A defects detection method based on A 0 mode and S 0 mode Lamb wave is proposed that "A 0 mode Lamb wave is used for defect determination by its amplitude variation in time domain, and utilized S 0 mode Lamb wave to locate the defect". In this paper, utilize GRUT to detect a via hole with a radius of 2 cm, the experimental results show that the proposed method is convenient and fast with less signal processing, and the experimental error is 10.22 %. [ABSTRACT FROM AUTHOR]